Chuck Jones and the 'rules'.

Chuck Jones made the Road Runner cartoons and from the first episode, he made an elaborate set of rules which are:

1. The Road Runner cannot harm or upset the coyote except by going 'Meep! Meep!'
2. No outside force can harm the Coyote, only his own ineptitude or the failure of Acme Products.
3. The Coyote could stop anytime - if he were not a fanatic.
4. No dialogue ever, except 'Meep! Meep!'
5. The Road Runner must stay on the road - otherwise, logically, he would not be called the Road Runner.
6. All actions must be confined to the natural environment of the two characters - The Southwest American Desert.
7. All materials, tools, weapons, or mechanical conveniences must be obtained from Acme Corporation.
8. Whenever possible, make gravity the Coyote's greatest enemy.
9. The Coyote is always more humiliated than harmed by his failures.